The present invention relates to a coupling for connecting a tubular pipework element with a pipe of plastics material engaged in said pipework element, the coupling being of the type comprising:
a peripheral locking gasket for the pipe, which gasket is adapted to extend around the pipe and is elastically deformable radially from a rest state in which it has a nominal inside diameter;
an outer clamping ring placed on the end of the pipework element and surrounding the peripheral gasket; and
axial thrust means for thrusting the clamping ring axially towards the pipework element, the facing surfaces of the clamping ring and of the gasket presenting associated cam surfaces adapted to compress the gasket centripetally onto the pipe when the clamping ring is thrust axially towards the pipework element.
The pipework elements in question can be pipes proper, flanged junction elements, or indeed piping accessories such as pipe fittings.
Such a coupling is intended in particular for connecting a tubular pipework element made of cast iron or of any other metal with a pipe having a smooth outside surface, and more particularly with a pipe made of plastics material such as polyvinyl chloride (PVC), polyethylene, or polypropylene, or with a pipe made of some other material.
In addition to providing sealing, such a connection coupling also serves to lock the pipe axially relative to the tubular pipework element, i.e. it prevents the two elements from moving axially relative to each other.
Such locking is provided by centripetal pressure being applied onto the peripheral gasket while the outer clamping ring is being subjected to axial thrust.
By way of example, such a coupling is described in document DE 30 02 205. In that document, the peripheral gasket is formed by a resilient split ring covered on its inside surface with hard engagement particles. Prior to assembly, the ring is engaged around the pipe and is held lengthwise thereon by means of its own resilience pressing the inside surface of the gasket against the outside surface of the pipe. To achieve locking proper, an outer clamping ring is screwed onto the tubular pipework element.
With a coupling as described in that document, it is necessary to position the locking gasket properly on the pipe before the pipe is engaged in the pipework element. The gasket must be positioned in the location that it is to occupy when it is finally installed on the pipe. Such positioning is relatively difficult to achieve since, prior to placing the pipe in the pipework element, it is difficult to foresee the exact position that the pipe will occupy within the pipework element.
An object of the invention is to propose a connection coupling enabling a pipe to be coupled to a tubular pipework element while accommodating great latitude in their relative axial positioning.
To this end, the invention provides a coupling of the above-specified type for connecting a tubular pipework element with a pipe engaged in the pipework element, the coupling including spacer means for holding the gasket spaced apart with an inside diameter greater than its nominal diameter prior to the pipe being put into place, which spacer means are releasable once the pipe is in place.
In particular elements, the coupling includes one or more of the following characteristics:
the gasket has at least one gap in its circumference, and the said spacer means include a removable spacer located initially in the gap, which spacer includes a handle extension that is accessible from outside the clamping ring;
around its circumference the gasket has at least two jaws that are curved and rigid, together with elastic return means for thrusting the two jaws centripetally;
the clamping ring has a notch in its inside surface for passing the handle extension of said spacer;
between the locking gasket and the end of the pipework element, the coupling includes resilient thrust means for thrusting the gasket axially away from the end of the pipework element;
the resilient thrust means comprise a washer that is axially expandable, at least in part;
the clamping ring has an inside groove for receiving the outside edge of said washer that is axially expandable, at least in part;
the pipework element has an internal peripheral groove and a sealing gasket disposed in the internal peripheral groove;
the axial thrust means include complementary thread elements formed on the clamping ring and on the pipework element;
the associated cam surfaces formed on the clamping ring and the gasket are frustoconical surfaces;
the clamping ring has a radial hole for receiving a pin for locking the clamping ring relative to the tubular pipework element, said hole being formed through the clamping ring so that when the clamping ring is placed on the end of the pipework element and is subjected to thrust from the axial thrust means the hole opens out along a locking abutment for the pin formed at the surface of the pipework element; and
the coupling includes a pin connected to said spacer.
The invention also provides a method of connecting a tubular pipework element with a pipe engaged in the pipework element, using a coupling comprising:
a peripheral locking gasket for the pipe, which gasket is adapted to extend around the pipe and is elastically deformable radially from a rest state in which it presents a nominal inside diameter that is smaller than the outside diameter of the pipe;
an outer clamping ring placed on the end of the pipework element and surrounding the peripheral gasket; and
axial thrust means for thrusting the clamping ring axially towards the pipework element, the facing surfaces of the clamping ring and of the gasket presenting associated cam surfaces adapted to compress the gasket centripetally against the pipe when the clamping ring is thrust axially towards the pipework element;
the method comprising the following successive steps:
holding said gasket spaced apart with a diameter greater than the outside diameter of the pipe, said gasket being in place axially in the coupling;
inserting the pipe into said gasket;
releasing said gasket so that it presses elastically around the pipe; and
thrusting the clamping ring axially towards the pipework element.